Generate valid python code if query param exists and requeststBody is required.

Fixed #322.

Author: ogis-yyamano

fastapi_code_generator/parser.py

@@ -330,7 +330,7 @@ def get_argument_list(self, snake_case: bool, path: List[str]) -> List[Argument]
         for argument in arguments:
             if positional_argument and argument.required and argument.default is None:
                 argument.default = UsefulStr('...')
-            positional_argument = argument.required or argument.default is not None
+            positional_argument = argument.required or (argument.default is not None) or argument.type_hint.startswith('Optional[')
 
         return arguments